1. Field of the Invention
This invention relates to papermaking fabrics, in general, and to dryer felts woven from cross-wrapped resin coated yarns, in particular.
2. Description of the Prior Art
In papermaking, the final stage in the process of removing water from a paper web is carried out in a papermaking machine's dryer section. In a typical papermaking machine, the paper web is dried by passing around a series of steam heated cylinders. A dryer felt or dryer fabric in the form of an endless conveyor belt ensures that the paper web is held in intimate contact with the heated cylinders. The dryer section may also employ hot air blowers, situated above or below the dryer felt. These blowers provide hot air, typically in the range of 500.degree. to 800.degree. F., to the paper web, contained on the dryer felt, to further aid in the removal of moisture from the paper web.
There is a tendency for dryer felts to physically and chemically degrade in the environment of high heat and high moisture concentration present in the dryer section. The degredation manifests itself in the form of dimensional variations, tearing or other destruction of the dryer felt. In addition, loss of fabric stability and loss of yarn stability is also manifested. It has been found that the edges of the dryer felt are most suceptible to destruction and degredation. In order to overcome these shortcomings, some paper mills use an air shower to cool the dryer felt after the paper web leaves the fabric. Air showers can also be used to cool the edges of the felt or fabric as it passes under or over the hot air blowers. Such showers, however, cannot cool the exposed edge right up to the paper sheet without disturbing the sheet, and there is, therefore, an area of fabric exposed to direct heat which cannot be cooled.
Even with the air shower, the best synthetic prior art dryer felts are rendered useless in a relatively short period of time. The replacement of a dryer felt is an expensive undertaking, both in terms of direct replacement costs, and machine downtime. There is thus a great need to extend the useful life of a dryer felt.